Homodinuclear f-f and Heterodinuclear f-p Lanthanide Helicates

Cobalt(II) Ions Connecting [CoII4] Helicates into a 2-D Coordination Polymer Showing Slow Relaxation of the Magnetization

The reactions of cobalt(II) perchlorate with a diazine tetratopic helicand, H₄L, in the presence of sodium carbonate afford two coordination polymers constructed from tetranuclear anionic helicates as building blocks: _∞³[Co₄L₃Na₄(H₂O)₄]·4H₂O (1) and _∞²[Co₅L₃Na₂(H₂O)₉]·2.7H₂O·DMF (2). The tetranuclear triple-stranded helicates, {Co^II₄L₃}^4-, are connected in 1 by sodium(I) ions and in 2 by sodium(I) and cobalt(II) ions (H₄L results from the condensation reaction between 3-formylsalicylic acid and hydrazine). The crystal structures of the two compounds have been solved. In both compounds the anionic helicates interact with the assembling cations through the carboxylato oxygen atoms. Compound 2 features chains resulting from connecting the tetranuclear helicates through cobalt(II) ions. The analysis of the magnetic properties of compounds 1 and 2 evidenced a dominant antiferromagnetic coupling for 1, resulting in a diamagnetic ground state. In contrast, the magnetic behavior of 2 is dominated at low temperature by the Co^II ion which connects the antiferromagnetically coupled {Co^II₄} helical moieties. The ac magnetic measurements for 2 reveal the occurrence of slow relaxation of the magnetization that is due to the single, uncorrelated cobalt(II) ions, which are diluted in an essentially diamagnetic matrix of {Co^II₄} moieties (ΔE_eff = 26.7 ± 0.3 cm^-1 with τ₀ = (2.3 ± 0.2) × 10^-6 s).

Lanthanide-directed synthesis of luminescent self-assembly supramolecular structures and mechanically bonded systems from acyclic coordinating organic ligands

Herein some examples of the use of lanthanide ions (f-metal ions) to direct the synthesis of luminescent self-assembly systems (architectures) will be discussed. This area of lanthanide supramolecular chemistry is fast growing, thanks to the unique physical (magnetic and luminescent) and coordination properties of the lanthanides, which are often transferred to the resulting supermolecule. The emphasis herein will be on systems that are luminescent, and hence, generated by using either visibly emitting ions (such as Eu(III), Tb(III) and Sm(III)) or near infrared emitting ions (like Nd(III), Yb(III) and Er(III)), formed through the use of templating chemistry, by employing structurally simple ligands, possessing oxygen and nitrogen coordinating moieties. As the lanthanides have high coordination requirements, their use often allows for the formation of coordination compounds and supramolecular systems such as bundles, grids, helicates and interlocked molecules that are not synthetically accessible through the use of other commonly used templating ions such as transition metal ions. Hence, the use of the rare-earth metal ions can lead to the formation of unique and stable species in both solution and in the solid state, as well as functional and responsive structures.

Tetrahedral MII based binuclear double-stranded helicates: single-ion-magnet and fluorescence behaviour

It has been demonstrated that the slow relaxation of magnetization can be achieved in high spin tetrahedral Co^II centres with an easy-plane magnetic anisotropy within the double-stranded helicates. The photoluminescence properties of the Zn analogues were studied in different solvents.

Container molecules based on imine type ligands

This chapter will give a short overview about container molecules, their synthesis and possible applications. The main focus is on those which are based on imine type ligands. These containers can be used for example for guest exchange, gas separation, as chemical sensors or for the stabilisation of white phosphorus under water. The described cages have wide openings or tightly closed ones. For one cage the reversible opening and closing is also described.